The present invention relates to optical spectrometry and more particularly to optical spectrometers incorporating an array of light emitting diodes as a broad band light source.
The invention described and claimed herein comprises a novel optical spectrometer using a light emitting diode array, controlled by novel multiplexing schemes in place of a conventional broadband light source.
To illustrate the operation of the invention, a spectrometer incorporating the novel device with an acousto-optic tunable filter (AOTF) will be described.
An AOTF is a birefringent crystal having a piezo-electric transducer bonded to it. Broad band light radiation passing through such a crystal can be diffracted into specific wavelengths by application of a radio-frequency driving signal to the transducer. The AOTF in combination with a broadband light source can be used as a part of an optical spectrometer, a tunable monochromatic light source or other optical instrument. When coupled to fiber optics, the AOTF can be located remotely from the sample of interest.
An AOTF is a solid state device and has several advantages over alternative spectroscopic techniques such as diffraction gratings, prisms, filter wheels or Fourier interferometer. The AOTF is rugged since it has no moving parts; it is compact, fast and can provide random access. These features allow AOTF-based optical instruments to be used in industrial environments for real-time, on-line process control, and for remote applications (including such extreme remote applications as planetary exploration).
To date, there has been no broadband light source of comparable advantage for use in such applications. Typically, the broadband light source is an incandescent lamp which needs to be replaced after several thousand hours of operation and is susceptible to malfunction due to mishandling or simply due to vibration. Typical lamps also consume considerable power and generate heat which must be dissipated.
Thus, the light source is the "weak link" in rugged-environment or remote sensing applications, since prior art devices rely on sources which are unreliable, inefficient, susceptible to damage, and require high power consumption and resultant heat dissipation.